Question

我是oop php的新手，并从某处复制了源代码，修改并测试它们。不知道新用户类有什么问题。

class DB {

    private $dbHost     = "127.0.0.1";
    private $dbUsername = "root";
    private $dbPassword = "";
    private $dbName     = "hihi";

    public function __construct(){
        if(!isset($this->db)){
            // Connect to the database
            try{
                $conn = new PDO("mysql:host=".$this->dbHost.";dbname=".$this->dbName.";charset=utf8",  $this->dbUsername, $this->dbPassword);
                $conn -> setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);

                $this->db = $conn;

            } catch(PDOException $e){
                die("Failed to connect with MySQL: " . $e->getMessage());
            }
        }
    }

    public function __destruct(){
        $this->db = null;   
    }

    public function display($sql){
        ..............
        return html_table;
    }

    public function insert($sql){
        ..............

    }
}

index.php //它不起作用

include 'DB.php';
include 'User.php';

$users = new User();
$users -> getAllUsers();

User.php //它不起作用

class User extends DB{
    public function getAllUsers(){      
    $sql = "SELECT * FROM userview WHERE event = 'a' ORDER BY created DESC";
    $users = $this->db->display($sql);
    echo $users;                
    }
}

致命错误：在C：\ Program Files（x86）中调用未定义的方法PDO :: display（）......

如果我将User.php更改为以下，

User.php //它不起作用

class User extends DB{
    public function getAllUsers(){      
    $sql = "SELECT * FROM userview WHERE event = 'a' ORDER BY created DESC";
    $users = $this->display($sql);
    echo $users;                
    }
}

致命错误：用户对象（[dbHost：DB：private] =＆gt; 127.0.0.1 [dbUsername：DB：private] =＆gt; root [dbPassword：DB：private] =＆gt; [dbName：DB：private] =＆gt; hihi [db] =＆gt; PDO Object（））

User.php //它不起作用

class User extends DB{
    public function getAllUsers(){      
    $sql = "SELECT * FROM userview WHERE event = 'a' ORDER BY created DESC";
    $users = display($sql);
    echo $users;                
    }
}

致命错误：在C：\ Program Files（x86）中调用未定义的函数display（）......

如果我不创建用户类，它就可以工作。

index.php //它有效

include 'DB.php';
$db = new DB();

$users = $db->display("SELECT * FROM userview WHERE event = 'a' ORDER BY created DESC");
echo $users;

我想创建类User，Company，....以扩展DB以便使用DB的类方法进行选择，更新，删除......但是会发生致命错误。 PLS。救命。非常感谢。

oop php新类用户扩展DB

0 个答案: